This invention relates to the type of reflector lamp commonly known as "PAR" lamps, an acronym for parabolic reflector lamps. These lamps are effective as spotlights or well controlled floodlights using simple parabolic reflectors behind an incandescent filament which is small enough to be treated as a point source. Such lamps as presently known are used in sockets and simple recessed fixtures, providing a relatively low cost installation, but with the known inefficiency of incandescent lamps, approximately 14 lumens per watt. It is known that circular gas discharge lamps may operate at luminous efficiencies of 40 to 50 lumens per watt with inductor ballasts, and up to 65 lumens per watt with inverter ballasts which operate the lamps at high frequencies. Circular fluorescent lamps are widely used in small lighting fixtures, and are also used in lampholder fittings such as those described in my U.S. Pat. Nos. 4,105,276 and 4,178,535. These lampholder fittings have bare, exposed lamps, and are usually designed for use within portable lamps fitted with lamp shades. Enclosing the lamp within a lampholder fitting has been unknown prior to this present invention, and my co-pending patent applications entitled "DECORATIVE GAS DISCHARGE LAMPHOLDER FITTING", and "LINEAR GAS DISCHARGE REFLECTOR LAMP".
These co-pending applications represent the first effective use of a gas discharge source, such as a fluorescent tube within a screw base supported lamp having any degree of optical control. The broad and diffuse nature of gas discharge sources, particularly circular sources, makes controlling the emitted light extremely difficult and requires careful design of both reflective and refractive elements in a common optical system. A simple paraboloidal reflector is inappropriate, as there is no luminous source at the focus. Also a conventional lenticular lens, commonly used in fresnel form to collimate small sources in such applications as automotive headlamps, relies on the existance of the luminous source at the lens focal point in order to function.
The principal purpose of this invention is to provide a reflector lamp employing a circular gas discharge lamp as a light source and having cooperating reflective and refractive optics to produce a relatively narrow light output beam. An additional co-pending patent application entitled "TRANSPARENT LIGHTING DIFFUSER FOR CIRCULAR GAS DISCHARGE LAMPS" describes one of the refractive techniques the inventor has found effective.